There exist already a series of articles of reclining furniture, in particular beds, which comprise a back member whose inclination is adjustable, so that a correct sitting position in the bed is rendered possible. In contrast to the relatively short head member which has been known for a long time, the back member extends over the entire length of the back and is pivotally jointed at the lower end. As shown in FIG. 1 of the accompanying drawings, in a known construction the back member 1 is connected by means of a pivot joint 2a, on both sides of the under-mattress, to a stationary middle member 3 which is securely fastened to the frame 4 of the bed. A thigh member 6 is connected to the middle member 3 by means of a further pivot joint 2b; the thigh member 6, in turn, is pivotally connected to a foot member, the second part of a two-part construction and is laterally guided in the frame 4 by means of pins 7. Lifting and lowering the movable members 1 and 6 is effected mostly by means of one or two motors (not illustrated).
In this kind of adjustable bed the back member 1 can therefore be moved to any desired inclined position by actuation of a motor, until the desired sitting position has been attained. However, as everybody knows from experience, this sitting position is not a fixed position which one assumes once and for all and then maintains. Because, on the one hand, the occupant of the bed will always have the tendency to slide on the middle member 3 in the direction of the arrow P; on the other hand, the rigid maintenance of a position once assumed is unpleasant in the long run, so that the occupant searches involuntarily for a change of position, even if it is merely a minor one.
Such a variation of the sitting position is practically impossible by means of the apparatus according to FIG. 1, unless a less comfortable and less advantageous position is accepted; namely the occupant's back is obviously fully supported only in the position in which he has slid completely backwards, his seat abutting the lower section of the back member 1. Any deviation from this position imports release from the supporting surface of the back member and thereby the tendency to strains and damage to the spine.
A further disadvantage of this known construction resides in that the upper mattress which is located on the under-mattress is severely angled in the region of the pivot joint 2a in the sitting position and slides on the under-mattress with every change of position of the occupant. It is thus very difficult for the occupant to find and maintain the anatomically correctly supporting position which is right for him.
What is therefore desired is an article of reclining furniture which permits a lying position and in addition thereto a perfect sitting position which adjusts itself automatically to the occupant upon minor changes of the sitting position and which ensures in every position anatomically correct support of his body.